Remove StringBuilder calls in CacheStorageDiskStore

https://bugs.webkit.org/show_bug.cgi?id=273657
rdar://127461376

Reviewed by Sihui Liu.

There are some dead stores to StringBuilder in CacheStorageDiskStore that should be removed.

* Source/WebKit/NetworkProcess/storage/CacheStorageDiskStore.cpp:
(WebKit::encodeRecord):

Canonical link: https://commits.webkit.org/278293@main

Source/WebKit/NetworkProcess/storage/CacheStorageDiskStore.cpp

@@ -500,12 +500,6 @@ static Vector<uint8_t> encodeRecord(const NetworkCache::Key& key, const Vector<u
     result.append(metaData);
     result.appendVector(headerData);
 
-    StringBuilder sb;
-    for (auto& data : bodyData) {
-        sb.append(data);
-        sb.append(",");
-    }
-
     if (isBodyInline)
         result.appendVector(bodyData);